MicroNugget: How to Configure NAT (PAT) on Cisco Routers

there are actually three major flavors of that out there static net dynamic net and that overload which most people call Pat and that's going to be what I talked about in this micro nugget now I'm not going to get too heavy into the concepts because my good friend Keith Barker has created a micro nugget talking about the NAT concepts as well so I'd encourage you to check that out I'm going to focus solely on the configuration here's our overview you've got a home or small office - where you've got the Cisco router connecting to the internet service writer that is bridging the gap between your internal world which has some internal scheme and if you're like every home in America you probably have one I do one six eight dot one dot something as your internal network which houses all your computers and servers and Xbox and whatever else you have running on your internal network and this is going to be the nat boundary that will be where our story begins I'm going to bring up a NAT router which all I've done is give it the host name I am NAT and give it the IP addresses that you can see here on this interface now I'm assuming that on this router fast ethernet 0/0 is plugged in to the internal network and fastethernet 0/1 is plugged into the internet both of them being fast ethernet interfaces because i'm assuming this is maybe a dsl or cox Wilcox's our service writer that will say cable modem a provider that is sitting out here on the internet so we've got those two connected I want a NAT from this side of the network network to this side first thing I need to do identify my interfaces I'm going to go into fastethernet 0/0 and type in IP NAT inside which says this is the inside interface that I'm connecting to now this is actually an emulated router on gns3 if this were a real router it actually hangs for about three seconds there gives you a heart attack if you're in a production environment don't worry it will come back I'm going to go into interface fastethernet 0/1 and type in IP NAT outside to tell it that's the outside interface no hang there now second step I need to create an access list that identifies which IP addresses are allowed to be translated now access lists could be a whole huge topic and then soft matter of fact it is I created an a micro now get just on standard access list which is what I'm going to use right here gonna do IP access lists stand which allows me to use a name and we'll say net these addresses that's just the name I decided to call it I'm gonna say permit and it says well what do you want to permit 192 168 dot one addresses of course my router I'm going to give it the wild card bits of 0 0 0 255 what on earth is that Bizzaro wild card bit got its name because it is exactly the opposite of the subnet mask now everybody knows 1 9 2 1 6 8 1.0 / 24 is really two five five two five five two five five zero but in bizarro land wildcard mask world its 0.02 at 0.25 five crazy Thank You Cisco so I'm going to back out it there it's done I now have this access list that identifies my internal IP addresses now it's time to put it all together with one magic command it is going to be IP NAT inside source list and then I type in the name of that list now I know right about now you're going would this was all good until you did that I'm going to explain this let me type the command and then I'll read it to you in plain English sourceless not these addresses out interface fastethernet 0/1 and overload it what did i just type I'm going to go back there and read it in English IP NAT that says cisco router i want an ad from the inside of my network out the source address is oh yeah those are identified in an access list not these addresses so I'm telling you not these addresses now destination I want to send them out interface and I'm falling off the edge interface fastethernet 0/1 and overload that see if I forgot that overload keyword it would only work for the very first person to get out and then it wouldn't share that outside address for anybody else in this case I want to overload it which is how we use Pat that's it actually uses ports to figure out how to share one IP addresses for multiple devices once I hit the enter key on that I am now configured for that it is ready to go there are actually many more nat configurations that you could do but that will get you up and running and get people surfing the internet which we all know will boost everybody's productivity right right anyhow if you'd like to see those other nat configurations please leave a comment at the bottom of this video of what you'd like to see and we'll see if we can create some micro for those for now my name is Jeremy Chara I hope this has been informative for you and I'd like to thank you for viewing what do you mean Internet access doesn't boost productivity

Channel: CBT Nuggets

Views: 76,791

Keywords: server 2016, windows server 2016, microsoft windows server 2016, microsoft training, it training, cbt nuggets, garth schulte, server 2016 training, mcsa server 2016, mcsa training, 70-740, 70-740 training

Id: rymxrGyiUp8

Length: 4min 40sec (280 seconds)

Published: Wed Feb 13 2013